Interpretive Summary: To address research needs in the medical and dental communities, the U.S. Department of Agriculture (USDA) Nutrient Data Laboratory (NDL) conducted a comprehensive study of the fluoride content of U.S. drinking water, as part of the US National Fluoride Database and Intake Assessment Study (NFDIAS). The NFDIAS is a collaborative effort of the NDL, the University of Minnesota, the University of Iowa College of Dentistry, and Virginia Polytechnic Institute and State University. A total of 288 samples in 144 locations across the U.S. and over two pickups were analyzed. Well water averaged <20 Fg fluoride per 100 g, municipal water averaged 100-110 Fg fluoride per 100 g, and the national average for all water sources is 71 Fg fluoride per 100 g. The fluoride database resulting from the national study will provide values on the fluoride content of tap water and other fluoride-contributing beverages and foods, support important research on public health research, and be of considerable value to USDA and other investigators in the US dental and medical research communities.

Technical Abstract:
The role of fluoride in reducing the risk of dental caries, especially among children, is well recognized and is the basis for current intake recommendations. The US Department of Agriculture, Nutrient Data Laboratory conducted a comprehensive study of the fluoride content of US drinking water, as part of the US National Fluoride Database and Intake Assessment Study, a collaborative effort with the University of Minnesota, the University of Iowa College of Dentistry, and Virginia Polytechnic Institute and State University. The sampling method involved: serpentine ordering of the US population by census region, division and county; dividing the population into 72 equal population size zones; and randomly selecting one county per zone and two residences per county. Participants were recruited by phone to provide two tap water samples, 3-4 months apart; samples (n=288) were analyzed by the direct read method. Well water, 18% of the samples, averaged <20 mcg fluoride/100 g, municipal water averaged 100-110 mcg fluoride/100 g, and the national average across sources was 71 mcg fluoride/100 g. These nationally representative data for drinking water will support public health research on the impact of fluoride on bones and teeth and will provide a foundation for assessment tools in the dental and medical communities.